1. Field of the Invention
The present invention relates in general to automotive steering systems and more particularly to a joint for connecting a steering shaft to a steering gear.
2. Description of the Prior Art
FIGS. 1 and 2 show, by way of example, a prior art steering system containing a steering wheel 10, a steering column assembly 12 and a rack and pinion steering gear 14. The steering column 12 has a steering shaft 16 rotatable with the steeing wheel 10, and the steering gear 14 has a pinion 18 and a rack 20 meshed with each other. The steering shaft 16 is connected to the pinion 18 by way of a cross universal joint 22 which is generally called a lower joint.
The lower joint 22 is provided with a yoke 24 connected by means of serrations to the pinion 18. In this connection, in order that dirigible wheels or front wheels of an automotive vehicle are turnable from a straight ahead position to the left and to the right by the same angle, it is required that a neutral position or midpoint position (a position intermediate between opposite lock positions) of the steering wheel 10 and therefore the steering shaft 16 corresponds to the straight ahead position of the front wheels, i.e., it is required that when the steering shaft 16 is placed at the midpoint position, the rack 20 is conditioned so as to be movable to the left and to the right by the same stroke S. It is therefore necessary to couple the steering shaft 16 and the pinion 18 at a predetermined relative position or phase.
FIGS. 3 and 4 show a prior art arrangement for installing the yoke 24 of the lower joint 22 in a predetermined relation to the pinion 18. The pinion 18 is formed with a groove 26 across the axis thereof. The yoke 24 has a tubular portion 28 of a U-like cross section, i.e., a tubular portion 28 having an axial slit 30 extending throughout the length thereof. The tubular yoke portion 28 also has a part-cylindrical serrated inner wall 32 where it is coupled with a correspondingly serrated end 34 of the pinion 18 and a pair of flanges 36 and 36 extending along the slit 30. The flanges 36 and 36 are respectively formed with bolt holes 38 and 40 which are axially aligned with each other to extend across the axis of the tubular portion 28 and therefore the axis of the pinion 18 and one 40 of which is threaded. A bolt 42 is allowed to pass through the bolt hole 38 and screwed into the threaded bolt hole 40 when the bolt holes 38 and 40 are aligned with the groove 26, i.e., the bolt 42 can be installed in place only when the pinion 18 and the yoke 24 are properly aligned with each other. The bolt 42, when installed in place, engages the groove 26 and prevents the pinion 18 or the yoke 24 from slipping off from the other.
Such alignment of the pinion 18 and the yoke 24 must be made by a trial and error method and therefore requires a relatively difficult and lengthy work, resulting in a high production cost. Further, positioning of the groove 26 must be accurate and therefore requires costly machining, resulting in a further increased production cost.
FIGS. 5 and 6 show another prior art arrangement for installing the yoke 24 of the lower joint 22 in a predetermined relation to the pinion 18. In this arrangement, the pinion 18 is formed with an annular peripheral groove 44 for engagement with the bolt 42 and an alignment mark 46 corresponding to the straight ahead position of the front wheels. The slit 30 of the yoke 24 corresponds to the midpoint position of the steering shaft 16. By coupling the pinion 18 and the yoke 24 in such a manner that the mark 46 is aligned with the slit 30, the steering shaft 16 and the pinion 18 can be properly aligned.
A disadvantage of the arrangement of FIGS. 5 and 6 is that the pinion 18 and the yoke 24 can be joined and fastened together by the bolt 42 even when they are not properly aligned, resulting in a possibility of misalignment and a necessity of readjustment.